The burgeoning electrical component industry is in constant need of easier and quicker methods of making electrical connections. With labor costs continually rising, there is a great desire to streamline these procedures and avoid unnecessary delays in production. One of the difficulties faced by those in the field is the problem of making a number of electrical connections in close proximity such as in computers and other complex electrical components. Many of these connections are quite small and the lack of adequate working area within the component is a source of many delays. Another factor that poses difficulty is the necessity of a secure electrical connection that is not affected by the jostling of daily operation. As a result, in many electrical components such as printed circuit boards and the like, there is a great need for a means of forming good connections quickly and with a high degree of conduction.
One useful method of forming a connection is used frequently in printed circuit boards. This method utilizes square or rectangular cross-section wire wrap posts as termination points. The end of a solid wire is stripped of insulation and with the aid of a winding tool the exposed conductor is tightly wound around the post approximately five complete turns. Tight winding of the wire provides excellent electrical contact at the corners of the post where the pressure of the conductor on the post is quite high. In some applications when a properly sized solid wire is so terminated, it is generally unnecessary to employ solder to ensure a reliable electrical connection. However, where a permanent connection is desired such a termination can be soldered.
Although this technique is reliable and quite effective for many applications, its feasibility is limited to solid wires. Stranded wires, unfortunately, do not remain tightly wound to the post and consequently produce unsatisfactory connections with this wire wrapping technique. This is in part because each strand of wire does not engage all four of the sharp edges on the post with each full turn.
Generally, solid wires do not withstand shock and vibration as well as stranded wires and in selected applications, such as in airborne electric equipment for example, there is a definite need for a method of satisfactorily terminating a stranded conductor to a wire wrap post on a printed circuit board.
A number of connectors have been developed to terminate a stranded conductor to a wire wrap post. Examples of such connectors can be found in U.S. Pat. No. 3,836,947 and U.S. Patent Application Ser. No. 497,709 filed Aug. 15, 1974, now abandoned, the disclosures of which are incorporated by reference herein. Solder can provide a high quality electrical and mechanical connection between a stranded conductor and a wire wrap post. However, positioning and holding the stranded conductor in the desired relationship with respect to the post during the soldering operation frequently presents serious problems. Limited space between a plurality of posts combined with the presence of other wires interfere with the use of tools, such as needle nose pliers, to fixture a stranded conductor to a post during soldering. Even though in some situations a stranded wire can be wrapped around a post to temporarily fixture the wire during soldering, this wrapping and soldering results in an unnecessarily bulky mass of material in the resulting connection. Thus the need for a simple means of forming a solder connection between a stranded conductor and a wire wrap post without the necessity of a hand-held fixturing tool to hold the stranded wire to the post is very substantial.
Electrical connections utilizing solder are well known. U.S. Pat. Nos. 3,239,125, 3,243,211, 3,525,799, 3,396,460 and 3,305,625, for instance, show different variations of solder rings or balls of solder within heat recoverable members useful in forming various electrical connections. Many connectors employing solder, however, are specifically adapted to the particular electrical components with which they are used. U.S. Pat. No. 3,312,772, for example, shows shield termination devices comprising a recoverable member, a solder insert and an insert comprising a metal foil. Similarly, U.S. Pat. No. 3,316,343 teaches connectors for use in joining flat electrical conductors with a flat rectangular solder insert. Terminal pins provided with solder that may be coated on the pin or deposited in a recess may be found in U.S. Pat. No. 3,324,230. Likewise, in U.S. Pat. No. 3,541,495 there is exhibited a coaxial contact for terminating both the central conductor and the braided shield of a coaxial cable with solder connections. Contact is provided with an internal sleeve of heat recoverable material having a solder insert. Other variations on this central theme may be found in U.S. Pat. Nos. 3,678,174, 3,721,749 and 3,852,517. The disclosures of each of these patents are incorporated herein by reference.